City of Chehalis, Regional Water Reclamation

Chehalis, Washington

Services Provided

Electrical Engineering
Mechanical Engineering


The City of Chehalis, WA constructed a new replacement waste-water treatment system for the entire community.

This will meet the requirement for discharges during the Chehalis River low-flow periods for the City to suspend discharges into the river. R&W’s largest SCADA infrastructure project, a Rockwell PLC with Wonderware HMI system. The plant design uses an SBR treatment system with UV disinfection. Large capacity equalization-storage basins provide for flow equalization and transition between operating discharge modes. During low river flow conditions the effluent is routed via tertiary sand filtration and then delivered to a land disposal area with a Poplar Tree plantation on the other side of the river.

The overall plant design has provisions for a future 100% increase in the SBR treatment process. In addition the waste solids will be treated using a sludge pasteurization process to accommodate land disposal. Wastewater flows are delivered via newly upgraded main pump stations off-site from the plant.